In 3GPP (3rd Generation Partnership Project), which is a project aiming to standardize a mobile communication system, carrier aggregation has been introduced (see Non-patent document 1). Furthermore, in 3GPP, the introduction of a dual connectivity has been discussed.
In the carrier aggregation and the dual connectivity, a user terminal performs radio communication with a radio access network by simultaneously using a plurality of carriers (a plurality of frequency bands). The plurality of carriers include a first carrier used for mobility control of the user terminal, and a second carrier that provides the radio communication in coordination with the first carrier.
In carrier aggregation, the scheduling in each carrier is performed by one base station (that is, one scheduler). In contrast, in a dual connectivity, the scheduling in each carrier is performed by different base stations (that is, different schedulers).